John Rambo. I had a similar problem about six months ago, and this is what I found to fix it.
You have two options at this point.
- Switch to Google Chrome. It now has a built-in version of flash.
- Check your software installation. A version of flash is available in the ubuntu-restricted-extras package, or kubuntu-restricted-extras, xubuntu-restricted-extras, etc.
The reason Youtube still works is because Youtube has added HTML5 support, which is built in to almost every browser (with the exception of Internet Explorer, which still doesn't fully support it as of version 9 or 10) since around 2009.
The flashplugin-installer package should be all you need, and that is installed with the restricted extras packages.
Please note that downloading and installing the .deb from Adobe does not work unless you move a file to Firefox's directory.
As was stated in the comments, there is no Firefox PPA, because no one needs one. Everything Firefox related that you would ever need is in the Ubuntu repositories or available through a Firefox extension.
The fix I recommend is installing Google Chrome JUST for Adobe connect, so long as Flash works well for everything else on Firefox.
chrome.google.com is the place to find it.